fix: handle bun child_process interop

Resolve execFile from named or default child_process exports so macOS Bun can load gitService in tests.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/git/gitService.ts

@@ -1,10 +1,32 @@
-import childProcess, { type ExecFileException } from 'node:child_process';
+import * as childProcessModule from 'node:child_process';
 import { promisify } from 'node:util';
 
 import type { ProjectGitChangeSummary, ProjectGitCommitSummary, ProjectGitContext } from '@shared/domain/project';
 import { nowIso } from '@shared/utils/ids';
 
-const execFileAsync = promisify(childProcess.execFile);
+type ExecFileException = import('node:child_process').ExecFileException;
+
+type ChildProcessModuleLike = {
+  readonly execFile?: typeof childProcessModule.execFile;
+  readonly default?: {
+    readonly execFile?: typeof childProcessModule.execFile;
+  };
+};
+
+export function resolveExecFileForInterop(
+  module: ChildProcessModuleLike,
+): typeof childProcessModule.execFile {
+  const execFile = module.execFile ?? module.default?.execFile;
+  if (typeof execFile !== 'function') {
+    throw new Error('node:child_process execFile is unavailable.');
+  }
+
+  return execFile;
+}
+
+const execFileAsync = promisify(
+  resolveExecFileForInterop(childProcessModule as ChildProcessModuleLike),
+);
 const GIT_TIMEOUT_MS = 5_000;
 
 type GitCommandRunner = (projectPath: string, args: string[]) => Promise<string>;

tests/main/gitService.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from 'bun:test';
 
-import { GitService } from '@main/git/gitService';
+import { GitService, resolveExecFileForInterop } from '@main/git/gitService';
 
 function createGitError(message: string, options?: { code?: number | string; stderr?: string }) {
   return Object.assign(new Error(message), options);
@@ -24,6 +24,24 @@ function createService(responses: Record<string, string | Error>) {
 }
 
 describe('GitService', () => {
+  test('resolves execFile from the named child_process export when available', () => {
+    const namedExecFile = (() => undefined) as unknown as typeof import('node:child_process').execFile;
+
+    expect(resolveExecFileForInterop({ execFile: namedExecFile })).toBe(namedExecFile);
+  });
+
+  test('falls back to default.execFile for Bun child_process interop', () => {
+    const defaultExecFile = (() => undefined) as unknown as typeof import('node:child_process').execFile;
+
+    expect(resolveExecFileForInterop({ default: { execFile: defaultExecFile } })).toBe(defaultExecFile);
+  });
+
+  test('throws when execFile is unavailable in both child_process export shapes', () => {
+    expect(() => resolveExecFileForInterop({})).toThrow(
+      'node:child_process execFile is unavailable.',
+    );
+  });
+
   test('describes a git repository with branch, dirty state, change counts, and head commit summary', async () => {
     const service = createService({
       'rev-parse --show-toplevel': 'C:\\workspace\\repo\n',